1. Field of the Invention
The present invention relates to a heat exchanger to which a connector for connecting an external piping to header pipes is integrally fixed by brazing to improve brazing work and to keep an appropriate piping connecting face, thereby improving reliability in connecting the connector to the piping.
2. Description of the Related Art
Generally, a parallel flow type heat exchanger has a plurality of tubes and fins alternately laminated, and header pipes are connected to and in communication with both ends of the laminated tubes. Top and bottom openings of each header pipe are closed by a blind cap, and partitions are located at required positions in the header pipes to divide the inside of the header pipes so that a heat exchanging medium meanders to flow a plurality of times between inlet and outlet connectors formed on the header pipes.
Such a heat exchanger is produced by temporarily assembling respective parts and integrally brazing them in a furnace.
Specifically, at least core portions such as flat tubes and header pipes, as the main portion for heat exchanging, are temporarily assembled. The temporarily assembled heat exchanger is entirely sprayed with a flux for brazing, placed in a furnace such as an electric furnace, and heated so as to be brazed into one body.
Respective steps of the above procedure are automated and arranged to co-operate by coupling with one another so as to produce a number of heat exchangers continuously.
From upstream to downstream of a conveying means using a belt conveyor, a temporally assembling step, a flux shower step, and an in-furnace integral brazing step are disposed sequentially. A temporarily assembled heat exchanger is placed in a stable state on the belt conveyer so as to be carried to the next step.
The flux shower step uses a suspension of flux or a solution prepared by mixing water and a low concentration of flux and sprays the solution in a mist state (spray) from above towards the entire body of the heat exchanger.
And, the flux shower is adjusted to a required minimum amount to cover the temporarily assembled heat exchanger entirely, thereby reducing the maintenance work on the production facilities.
If a large amount of flux is used, the flux drips from the heat exchanger to the conveyor belt below, and the drops harden to contaminate the surface of the heat exchanger and the belt conveyor. By spraying a minimum amount of flux in a low concentration, such contamination is minimized.
It has been known recently to reduce costs by using brazing on connectors which supply and receive a heat exchanging medium to and from an external apparatus, to header pipes (e.g., Japanese patent application Kokai No. 6-281387). Such connectors are often made large enough to serve as mounting brackets for the heat exchanger, with threaded fastening holes.
But, in the flux shower step described above, this connector has the flux adhered in clusters on its surface for connection to the piping and the surface smoothness is degraded, so that the connector and the external piping are not closely connected to each other, leaking the heat exchanging medium.
In view of the above, as shown in FIG. 10 (1), when a heat exchanger 21, which is temporarily assembled by alternately laminating a plurality of tubes 22 with fins and connecting header pipes 24, 24 to and in communication with both ends of the laminated tubes, is laid down in a brazing posture and a flux is sprayed from above (indicated by arrows F in the drawing), a connector 28 is temporarily covered with a cap-shaped protecting member 28A to cover at least the entire piping connecting face, so that the flux does not adhere to the piping connecting face.
Besides, in the case of a heat exchanger for vehicles, a connector is disposed in a direction along both sides of the heat exchanger, or a connector is disposed in a different direction because of a space for mounting the heat exchanger or an arrangement of piping in the vehicle. For example, the heat exchanger is produced with a connector disposed to face downward when the heat exchanger is in the brazing posture.
However, in the case of the connector of the above-described conventional heat exchanger, the connector is disposed to face downward when placed in the brazing posture, and the flux is not directly showered to the piping connecting face of the connector. But, regardless of the protective cap, the flux dropping from other parts of the heat exchanger may reach the piping connecting face to contaminate it.
Specifically, as shown in FIG. 10(2), even if the cap-shaped protective member 28A is put on the connector 28, the flux permeates into the gap of the piping connection faces between the protective member 28A and the connector 28 to contaminate the piping connecting faces. Especially, since an excess portion of the sprayed flux tends to flow down along the surface rather than dropping directly from the sprayed location, it is highly probable that the flux accumulates on the connecting surface of the connector 28 directed downward.
And the protective member may have higher airtightness and higher adhesion or a shape to entirely cover the connector. But, the protective member cannot be attached and removed easily and must be designed for each connector having a different shape, causing a disadvantage in view of costs.
Besides, a step may be added to the series of automated steps to remove the flux adhered to the piping connecting face of the connector, but it is not preferable because the production facilities become large in scale and the production cost increases.